A need exists for improved chemical formulations that are effective for inhibiting clay swelling, particularly when conducting drilling, fracturing, or other operations in shale formations. Shale formations are rich in clay content. They are horizontally drilled and then hydraulically fractured in multiple stages. Clay is by nature hydrophilic and in the presence of water it tends to absorb water and swell. In some cases it may even disintegrate. During the drilling process, this may cause the hole to cave or cause the drilling cuttings to disintegrate into fines, which cannot be removed easily on the surface from the drilling fluid. During hydraulic fracturing, clay swelling may negatively affect production due to formation embedment in the proppant pack.
Water-based drilling fluids (muds) typically comprise a mixture of water and clay (e.g., bentonite) and also commonly include clay inhibitors and/or other chemicals. The drilling fluid is circulated through the well bore during drilling in order to lubricate and cool the drill bit, flush the cuttings out of the well, and strengthen the sides of the hole to prevent cave-ins. Typically, the drilling fluid is delivered downwardly into the well through the drill string and then returns upwardly through the annulus formed between the drill string and wall of the borehole.
Hydraulic fracturing fluids typically comprise water and sand, or other proppant materials, and also commonly include various types of chemical additives. Examples of such additives include: gelling agents which assist in suspending the proppant material; crosslinkers which help to maintain fluid viscosity at increased temperatures; gel breakers which operate to break the gel suspension after the fracture is formed and the proppant is in place; friction reducers; clay inhibitors; corrosion inhibitors; scale inhibitors; acids; surfactants; antimicrobial agents; and others. The hydraulic fracturing fluid is pumped into the subterranean formation under sufficient pressure to create, expand, and/or extend fractures in the formation and to thus provide enhanced recovery of the formation fluid.